I posted already the suggestion for such stage but now I can confirm it works and it works fine. I tried it in my TDA1541A non-o/s DAC and it was better than the other things I tried which include a few classic opamp I/Vs and passive resistor I/V followed by the tube stage. Application is similar to that suggested by Kuei for the OPA660.

If used with JFET with Idss of 10-12mA, values between 200 and 500 Ohms for VR1 should be fine. Trimming should be redone after a few minutes of warming up.

Vuki had reported a successful implementation of this stage (without current injection) in the AD1865 DAC.

Just wanted to say – though in the meantime I did have certain number of hits on my DAC page, I am completely disappointed by the reaction of The Forum. Ok, I know it happens that the people sometimes stay silent about the things they are in fact interested for, but…

Some interesting things I have dug lately.

http://www.stereophile.com/printarchives.cgi?840
I might be out of time, but I’ve never before heard for (or listened to) Ayre. In the review it was mentioned that the AD844 is used without feedback and the spectral content of the measured distortion is similar to those graphs I uploaded.

Another interesting case. Krell KAV-CD250 comprises AD844 and the trimmer (btw the same BI 67 you might note in my DAC) is aboard. The fact the trimming is done here and not downstream (I don’t see a coupling caps, hence it should be done somewhere) may and may not be related to the fact the AD844 is used as a common base since the PCM1702 puts out a bipolar (+/-) current. But if it is used this way, I’d expect to see the trimming circuit exactly here. The pictures I found are here:http://www.webmedia.pl/maciejza/tuning/krell.htmhttp://www.webmedia.pl/maciejza/tuni...ell/krell9.jpg
Unfortunately I don’t have any further info about this player. Fyi, the AD844 used like a classic I/V opamp is good but not spectacular.

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No. I’ll compare it to some discrete (single end, not symmetrical) common base stages next weeks but OPA660 should wait a bit. Circuits are similar but in fact it will be easier to make a new board for the OPA660 than to change this I have with AD844.

Originally posted by Pedja No. I’ll compare it to some discrete (single end, not symmetrical) common base stages next weeks but OPA660 should wait a bit. Circuits are similar but in fact it will be easier to make a new board for the OPA660 than to change this I have with AD844.

I meant originally that both OPA627 and AD826 can be used exclusively as a classic IV opamps.

As about the secret chip, I found this:
“The Reference DAC modules are based on the highest grade of the new 24-bit, multi-bit Burr Brown1 1704 DAC and OPA627AP I-to-V converters.”http://www.marklevinson.com/products...-6&details=yes
And in fact it looks like it is BB.

I've built a DAC using paralleled 1704 K DACs, but the non-oversampling TDA1543 sounds better to me.

If it wasn't for all that NIGC controversy I would be bulding a DAC using 1541S2 chip right now

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“Do something really well. See how much time it takes. It might be a product, a work of art, who knows? Then give it away cheaply, just because you feel that it should not cost so much, even if it took a lot of time and expensive materials to make it.” - JC

From the Strereophile’s test, one (me for example) could realize that ML invented something regarding the DAC chip and swapped the previous one with some their own module. Actually (if I am not again mistaken), the module comprises BB DAC chip and output stage, just like the previously used UltraAnalog's DAC (I guess) incorporates the DAC (strictly speaking) and the IV stage.

Don’t know about the PCM1704, but while we are at BB, compared against the SM5842/PCM63K, the TDA1543 non-o/s lacked some dynamics (and this was probably related to the fact the later used a resistor only I/V) but many other things, let’s say musicality, were on its side (I think I wrote this already somewhere).